1. Technical Field of the Invention
The present invention relates to a transformer to be applied to a switching power unit for charging a battery group in, for example, an electric automobile, and more particularly to a multi-channel uniform output type transformer for obtaining output at the same level from a multiplicity of secondary windings.
2. Description of the Prior Art
In, for example, the electric automobile, a power source obtained by series connecting as many secondary batteries as 200 or more is used as a driving power source. It is not simple to uniformly and efficiently charge these many batteries, but concerning a charging system, various technical development has been pursued. As one of them, such a charging system as shown in FIG. 11 has been proposed.
According to this system, the multi-channel uniform output type transformer 1 is used for a charging apparatus, and each channel output 31 of the transformer is connected in parallel to each battery 21 of a series battery 20 to individually charge each battery 21.
As described above, a driving power source for electric automobiles is obtained by connecting 200 or more secondary batteries in series. If, therefore, each single battery 21 has a difference in capacity because of an individual difference of each battery 21, temperature distribution within a packed battery 20 and the like, the electric power of some batteries having smaller capacity becomes the electric power of each battery to shorten the life of the batteries. In other words, even if there is any slight difference in capacity between each battery, it can lead to big power loss as a whole. Therefore, it is important in the multi-channel uniform output type transformer to make the output voltage of each channel uniform with a very high degree of accuracy.
In addition to the above described problem to make the output voltage uniform, there is also a problem in the manufacture that a conductor to be used for the secondary winding must be wound a number of times corresponding to the number of output channels. More specifically, if as many conductors as 200 are wound round the core at the same time, it becomes difficult to distinguish a winding start from winding close of each conductor, and to bring a pair of output ends of one conductor into correspondence with each other. Further, since lead pins are normally connected to the starting end and closing end of each conductor, the cost required for the process will become higher.
Therefore, it is an object of the present invention to provide a multi-channel uniform output type transformer capable of making the output balance of each channel very uniform, and contributing to reduced cost by simplifying the winding process.
The present invention relates to a multi-channel uniform output type transformer, and according to a first aspect of the invention, there is provided a multi-channel uniform output type transformer wherein a secondary winding is a flat cable belt comprising covered conductors corresponding to a number of the output channels arranged in parallel, a plane loop member is formed by appropriately folding the flat cable belt, and this plane loop member is arranged so as to substantially orthogonally intersect the winding shaft of the core.
According to a second aspect of the invention, there is provided a multi-channel uniform output type transformer wherein the plane loop member is formed by folding the flat cable belt odd-numbered times. According to a third aspect of the invention, there is provided a multi-channel uniform output type transformer specified in the second aspect, wherein the plane loop member is formed by overlapping the winding start and winding close end portions of each conductor included in the flat cable belt in such a manner that the both end portions are adjacent to each other respectively.
According to a fourth aspect of the invention, there is provided a multi-channel uniform output type transformer wherein a plurality of the plane loop members are formed by a plurality of the flat cable belts, and each plane loop member is arranged so as to become substantially concentric circle-shaped on the same plane substantially orthogonal to the winding shaft. According to a fifth aspect of the invention, there is provided a multi-channel uniform output type transformer wherein a plurality of the similar plane loop members are formed by a plurality of the flat cable belts, and each plane loop member is arranged in deviated relationship with each other in parallel in directions that are substantially orthogonal to each of interlinkage magnetic field loops induced on the core by the winding shaft and the primary winding.
According to a sixth aspect of the invention, there is provided a multi-channel uniform output type transformer wherein the flat cable belt is supported at the farthest position from a gap of the core.
According to a seventh aspect of the invention, there is provided a multi-channel uniform output type transformer wherein a collectively pressure welding type flat cable connector is fixed on a substrate and at least one end portion of the flat cable belt is connected to the connector.
According to an eighth aspect of the invention, there is provided a multi-channel uniform output type transformer wherein axial type diodes of the same number as the number of the output systems are substantially vertically installed and fixed on the substrate, and one lead pin of the diode on the cathode side or the anode side is installed on the substrate while the other lead pin is connected to each conductor of one end portion of the flat cable belt. According to a ninth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in the eighth aspect, wherein diodes of the same number as the number of the output systems are integrated in a line for each diode of an appropriate number to be divided into a plurality of diode rows, each diode row is vertically provided on the substrate at appropriate intervals in parallel with each other, and one end portion of the flat cable belt is appropriately cut, and each of the conductors is connected to a predetermined diode of the appropriate diode rows.
According to a tenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in any of the above described seventh to ninth aspects of the invention, wherein the substrate is used as a printed circuit substrate, the circuit substrate concerned is supported by the winding shaft portion of the core, and the plane loop belt is arranged on this circuit substrate surface.
According to an eleventh aspect of the invention, there is provided a multi-channel uniform output type transformer wherein the primary winding and secondary winding are used as a sheet coil. In the eleventh aspect of the invention, the primary winding is a primary sheet coil comprising one printed circuit formed in a loop shape or in a helical shape on the substrate; the secondary winding is a secondary sheet coil, comprising folded printed circuits, which correspond to patterns obtained by folding back printed circuits corresponding to the number of output channels, alternately formed on the front and back surfaces of the substrate, and comprising the folded printed circuits continuously connected via a throughhole for each output channel; and each of these sheet coils is stacked and arranged so as to substantially orthogonally intersect the winding shaft of the core.
According to a twelfth aspect of the invention, there is provided a multi-channel uniform output type transformer wherein the secondary sheet coil is formed by a multi-layer substrate. Concretely, the secondary winding is a stacked substrate type secondary sheet coil comprising printed circuits corresponding to the number of output channels continuously connected via throughholes while the printed circuits are being formed into folded patterns in each layer of the multi-layer substrate.
According to a thirteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in the eleventh or twelfth aspect of the invention, wherein when a printed circuit formed on a certain surface of the substrate is connected to a printed circuit of the folded pattern formed on another surface, a number of times of folding in the secondary sheet coil is counted, and the number of times of folding is set to an odd number.
According to a fourteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in any of the eleventh to thirteenth aspects of the invention, wherein the printed circuit pattern of the secondary sheet coil is a line-symmetrical diagram as it is seen through from one substrate surface.
According to a fifteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in any of the eleventh to fourteenth aspects of the invention, wherein the primary sheet coil is pinched between the two secondary sheet coils described and the distance between each sheet coil is made constant.
According to a sixteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in the fifteenth aspect of the invention, wherein the primary sheet coil is arranged in coincidence with the position of a gap of the core.
According to a seventeenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in the fifteenth or sixteenth aspect of the invention, wherein the printed circuit patterns of the two secondary sheet coils for pinching the primary sheet coil therebetween are plane-symmetrical to each other with respect to the primary sheet coil.
According to an eighteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in any of the fifteenth to seventeenth aspects of the invention, wherein lead pins are vertically provided on both sides of the substrate of the primary sheet coil, the lead pins concerned are inserted through positioning hole portions formed on the two substrates of the secondary sheet coils for fixing, whereby a distance between each sheet coil is maintained to be the predetermined distance.
According to a nineteenth aspect of the invention, there is provided a multi-channel uniform output type transformer specified in any of the eleventh to eighteenth aspects of the invention, wherein plane packaging type diodes of the same number as the number of output systems are packaged on one surface of the substrate of the secondary sheet coil, and one lead terminal on the cathode side or on the anode side of the diode is connected to a printed circuit portion corresponding to the end portion of the secondary winding on this packaged surface.
In this nineteenth aspect of the invention, there are some cases where the winding start end portion and the winding close end portion of the secondary winding are separated into the front and back surfaces of the substrate respectively to be formed, such as when the secondary sheet coil is folded odd-numbered times. According to a twentieth aspect of the invention, there is provided a multi-channel uniform output type transformer, wherein two lead terminals (anode and cathode) of the diode are connected to printed circuit portions corresponding to the winding start end portion and the winding close end portion of the secondary windings of their respective adjacent systems via the throughholes formed on the substrate.